A few fsharp-analyzers suggestions

[Numpsy]

I tried running the Expecto library code through a few fsharp-analyzers, and got a few suggested changes.
These ones are from https://g-research.github.io/fsharp-analyzers/analyzers/VirtualCallAnalyzer.html where it suggests replacing Seq functions with explicit types when the collection types are fixed:

Expecto.Impl.fs(963,11): Warning GRA-VIRTUALCALL-001 : Consider replacing the call of Seq.tryFind with a function from the Array module to avoid the costs of virtual calls.
Expecto.Impl.fs(972,47): Warning GRA-VIRTUALCALL-001 : Consider replacing the call of Seq.find with a function from the Array module to avoid the costs of virtual calls.
Expecto.fs(546,12): Warning GRA-VIRTUALCALL-001 : Consider replacing the call of Seq.fold with a function from the List module to avoid the costs of virtual calls.

Any thoughts?

[farlee2121]

I don't see any issue with this. It's not affecting any type inference.